1. Field of the Invention
This invention relates to a vice for adjusting the position of stationary and movable clamp elements to the required position on the worktable of a working or handling machine. This invention also relates to a vice having a piston-cylinder assembly for driving the movable clamp element towards the stationary clamp element, to securely and firmly hold a work therebetween.
2. Description of the Related Art
A conventional vice, which holds a work between a pair of clamp elements, is generally fixed in place on the worktable of a working or handling machine. As a result, the vice cannot move the work lengthwise or crosswise on the worktable, nor rotate it to a desired position thereon. When this type of vice is fixed on the worktable of, for example, a small drilling machine, and the worktable itself is fixed, i.e. non-movable/non-rotable, the base of the vice must then be fixed on the worktable at exactly the desired position. Accomplishing this demands special skill.
When the work is displaced from the desired working or handling position, the vice must be readjusted until the work is back in position. Further, when, in the course of processing, the work is set at a plurality of positions or when it is replaced by another work, the position of the base of the vice on the worktable must be changed. The fixing of the vice on another position on the worktable also requires considerable skill and is, moreover, a time-consuming process.
The authors of this invention have developed a vice which comprises a base which is fixed on the worktable of a working or handling machine, a slider which can slide on the worktable and is provided with a stationary clamp element and a movable clamp element, as well as a pressurized-fluid operated unit for fixing the slider to, and disconnecting the same from the base by operating a foot-pedal. In addition, the authors have succeeded in improving the fixing efficiency of the vice, making this a much less protracted operation.
However, when this improved vice is fixed on the worktable of a working machine such as a boring machine, and where the operator uses, say, his right hand to adjust the slider, and his left hand to operate the handle for lowering the working head, there is a danger that the cutting tool mounted on the working head will touch the operator's right hand, causing him potentially serious injury.
The British Patent Specification No. 1,197,674 discloses a vice which comprises a lead screw for selectively moving the movable clamp element toward and away from the stationary clamp element, and a reciprocating piston-cylinder assembly having pistons arranged in series for reciprocating the lead screw in its axial direction.
This piston-cylinder assembly comprises a housing, members arranged in series in the axial direction of the housing and forming piston chambers between the adjacent members, and pistons each fitted in its respective member. The resultant force of the pneumatic pressures exerted on the pistons drives the lead screw via a piston rod carrying the pistons and connected to the lead screw in an end-on manner, whereby a work is clamped between both clamp elements. Compressed air is forcibly supplied to the corresponding piston chambers via a duct formed in the piston rod, in order to reciprocate the piston assembly.
Since the maximum distance between the stationary and movable clamp elements is substantially equal to the maximum diameter or the maximum width of the work to be clamped between the clamp elements, the maximum traveling length of the lead screw must be equal to the maximum distance. Accordingly, the vice according to the British Patent has the maximum dimension along the lead screw equal to the length of the lead screw plus that of the piston-cylinder assembly, resulting in a bulky construction. Further, with this vice, changeover valves must be prepared for the movement of the piston mechanism in one direction and in the opposite direction thereto, respectively. Thus, the fluid control system becomes complicated.